The embryonic face begins as similarly sized buds of tissue that surround the primitive oral cavity. The buds of mesenchyme encased in epithelium (primordia) grow out differentially to form the distinctive facial profile. The long term objective of this proposal is to understand the mechanisms behind the development of normal, face shape. One of the prime factors determining facial morphology is the differential growth of the embryonic primordia. The aim of this project is to focus on the role of basic fibroblast growth factor (BFGF) in the differential growth of the facial primordia in vivo. Previous work has demonstrated a specific effect of BFGF on growth of facial mesenchyme in vitro and this project is an extension of these earlier experiments. The proposal will concentrate on normal face development, and subsequent work will exploit the retinoic acid-induced cleft lip embryos. Ultimately the early molecular events leading to facial clefting will be studied in the cleft chick embryo face. The experiments planned will address: a) the expression of BFGF proteins and BFGF receptors in facial mesenchyme; b) the location and timing of expression of FGF proteins; c) the distribution of heparan sulfate proteoglycans in the face since HSPG could be a major reservoir for extracellular BFGF; and d) the effects of locally released BFGF on chondrogenesis in the upper beak. The results of these experiments will either support or refute the hypothesis that differential growth of the facial primordia is the result of differences in responsiveness to growth factors and/or differences in local concentrations of growth factors.